1. Field of the Invention
This invention relates to computer interface circuitry and, more particularly, to methods and apparatus for providing a single interface by which a computer may connect to any of a plurality of different peripheral devices which handle information in a plurality of different formats.
2. History of the Prior Art
Computers offer many possible formats in which data may be utilized. For example, some of the earlier personal computer processors were only capable of handling data presented to them in eight bit units. Later computer processors were capable of handling data in sixteen bit units. More recently designed computer processors are capable of handling data in thirty-two bit units, and the more advanced computers are capable of handling data furnished in sixty-four bit units. Often, these formats are a natural outgrowth of the particular information or the manner in which it is handled. For example, industry standards assure that information will be available in certain formats; IEEE standards for floating point numbers are thirty-two or sixty-four bits while ASCII characters are typically eight bits.
When a computer is connected to a peripheral device, the computer must be able to utilize the data provided by that device. This requires a computer which normally handles data in one particular format to communicate with peripheral devices which handle data in other formats. In general, a computer should be capable of communicating in all formats used in earlier models of the product line of the manufacturer. In this way, software and hardware designed for use with earlier models of the product line having lesser capabilities may be run by improved computers in the product line.
Normally, the ability to communicate with peripheral devices operating in other formats is provided by special circuit arrangements which are built into the peripheral devices and convert information furnished in a native format to the format of the computer. Each such arrangement is adapted to handle a particular format conversion. Consequently, when a piece of peripheral equipment operating in a particular format is to be used with a particular computer system utilizing a different format, circuitry must be provided for converting between the formats before the equipment can be utilized. Often the design of such conversion circuitry is so expensive that the two pieces of equipment are never used together.
Even when circuitry is provided for format conversion as a part of a peripheral device, the total cost of the computer system rises because of the specialized nature of the converting circuitry. It is much more cost effective if the same converting circuitry can be used with all peripheral devices so that its design and manufacturing costs are spread over a much larger base.